The present invention relates to power tools and, in particular, to tools of the type powered by a detachable battery pack. The application relates in particular to impact tools, such as impact wrenches or other torque-applying impact tools.
It is known to provide powered torque-applying tools with means for controlling or limiting the torque applied by the tool to prevent over-torquing of fasteners or the like. These torque-limiting techniques typically utilize fairly complex and expensive mechanical, electromechanical or electronic devices for measuring applied torque and comparing it to a predetermined reference torque level. Such techniques are capable of providing fairly precise torque limiting or control.
However, it is frequently acceptable or desirable to provide a fairly rough or coarse torque limiting function in applications where precise torque control may not be necessary. It is known to provide impact tools with a built-in acoustic or vibrational detector, such as a microphone, to detect the sounds of impacts generated by the tool when torque starts to build up. One such device is disclosed, for example, in U.S. Pat. No. 5,277,261, which counts the number of impacts and disconnects power from the motor after a predetermined number of impacts has been counted. However, in order to utilize this feature, a person must purchase a tool of the type which incorporates the feature.
This application is directed to electrically-powered devices and power packs therefor which avoid the disadvantages of prior devices while affording additional structural and operating advantages,
An important aspect is the provision of a technique for simply and economically providing a pre-existing device with an acoustically triggered control function.
In connection with the foregoing aspect, another aspect is the provision of a combination of an electrically powered device and a removably connectable battery pack therefor, wherein the acoustically-triggered control function is incorporated in the battery pack.
Another aspect of the invention is the provision of a battery pack of the type set forth.
A still further aspect is the provision of a method for acoustically controlling shutoff of an electrically-powered impact tool.
Certain ones of these and other aspects may be attained by providing a battery pack for an electrically-powered device, the battery pack comprising: a housing; a battery disposed within the housing; a connection circuit for electrically connecting the battery to the associated device; and a control circuit in the housing connected to the connection circuit for controlling operation thereof, the control circuit including a detector for detecting vibrations generated by the associated device in use and producing a control signal, and a timer responsive to the control signal for initiating a predetermined time period, the control circuit being operable for disconnecting the connection circuit at the expiration of the time period.